The JPL HORIZONS on-line solar system data and
ephemeris computation service provides access to key solar system data and
flexible production of highly accurate ephemerides
for solar system objects
177 planetary satellites,
the Sun, L1, L2, select spacecraft, and system barycenters
HORIZONS is provided by the Solar System Dynamics Group
of the Jet Propulsion Laboratory.
The HORIZONS system can be accessed using any of the following methods:
||Although the web-interface to HORIZONS
provides nearly all capabilities of the primary
telnet interface (and email interface),
it does not provide the following:
- Small-body PARAMETER-MATCHING population searches
(use the small-body search engine as an alternative)
- Integration of USER-INPUT ORBITS
- SPK BINARY FILE production
- CLOSE-APPROACH TABLES
- (updated 2013-Apr-04)
Complete documentation is available in the following formats:
Documentation is also available on-line
using the telnet interface to HORIZONS
'?' from any prompt).
New users of the
web-interface to HORIZONS may want to consult
this tutorial first.
HORIZONS system news
is also available describing recent changes and improvements.
Using the telnet Interface
The HORIZONS system can be accessed directly by connecting to
"horizons.jpl.nasa.gov" via telnet port 6775.
This will initiate a text-only "VT100" terminal session that accesses
all HORIZONS functions.
You will be taken through a series of prompts that will ask you questions needed to
generate the desired information.
To initiate such an interactive session from a UNIX/LINUX system command line, type:
telnet horizons.jpl.nasa.gov 6775
Most MacOS and Windows telnet programs have a dialog box in which
the port number (6775) can be entered.
If after connecting to "horizons.jpl.nasa.gov" you are prompted for a
login name (not necessary for HORIZONS),
it means the port 6775 request was not passed along by the software on your end.
Some Windows terminal software does not fully implement the telnet protocol and does
not send port numbers, even if you enter them.
If your connection is refused, it is likely due to a firewall or security
restriction at your end. In either case, please contact your local computer
system administrator or consult your telnet program documentation if you need
more help. Since no password or security information is exchanged, you may be
able to request a firewall exception from your institution.
A HORIZONS terminal session can also be started from within a web-browser, by
entering this URL in your browser:
If this URL does not open a session, your browser is not configured
for telnet, and you will have to use the command-line method above,
or web HTML or e-mail interfaces.
Using the email Interface
The HORIZONS system can be accessed using email to submit batch-style input files.
Instructions on how to access the email server,
including a complete detailed example, is available by sending an email message to
with the subject "BATCH-LONG".
Alternatively, you can access the instructions via FTP.